do gut bacteria prevent allergies?

Intestinal tracts of germ free mice and mice given clostridia bacteria. The higher levels of mucus in the clostria tracts is thought to prevent allergens from leaking into the bloodstream.

Science News brings word of a recent PNAS report on gut bacteria and allergies. In the study, researchers gave a group of mice antibiotics to wipe out their gut microbiome. Feeding the mice peanuts after this treatment seemed to induce allergy-like responses, that weren’t observed in mice who didn’t receive the treatment. The researchers gave the mice Clostridia bacteria to replenish the microbiome, and the response diminished.

Cathryn Nagler of the University of Chicago and colleagues treated some mice with antibiotics to wipe out the animals’ gut bacteria, and then triggered an allergy-like response to peanut particles. Peanuts revved up the germ-free animals’ immune systems — but mice with normal gut bacteria didn’t have the bad reaction.

Giving germ-free mice a dose of Clostridia bacteria made the animals more like their counterparts with normal gut flora. The microbes encourage mouse cells to make mucus that helps seal up the intestines, keeping food particles from slipping into the bloodstream and riling up the immune system, the researchers found.

The researchers suggest that this might also hold true for humans.

carbs fuel colon cancer in mice

Carbohydrate rich diets, especially refined carbohydrates, have been linked to higher rates of colon cancer in the developed world, when compared to developing nations. A new report in the journal Cell provides insight into how this might come to be. Science News explains:

To probe the link between colon tumors and gut microbes, the researchers treated mice engineered to be prone to colon cancer with antibiotics. By eradicating intestinal bacteria, the drugs hindered malignant lumps of cells called polyps from growing in the lining of the colon and small intestines. The team then noticed that feeding the rodents a diet low in sugar and starch also reduced the growth of polyps.

The mice had two gene mutations often linked to colon cancer in people,one of which derails a cell’s ability to fix errors that arise during DNA replication, known as the mismatch DNA repair system.

A mismatch repair deficiency causes cells in the lining of the colon to divide quickly, explains study leader Alberto Martin, an immunologist at the University of Toronto. Bacteria and carbs speed the process, he says, damaging the genome and leading to tumor growth.

The researchers surmised that when microbes feast on carbohydrates, the germs must produce a chemical that pushes colon cells lacking the ability to repair DNA mismatches toward uncontrollably multiplying into tumors.

The researchers discovered that gut bacteria process carbohydrates into butyrate, which can induce cancer in  APCMin/+MSH2−/− mice by allowing cancerous  MSH2−/−cells to proliferate uncontrollably in the colon.



benefits of water fluoridation

govt water fluoridation

Water fluoridation programs re-emerge as a controversial topic from time to time. Just last year it was a hotly debated topic in Portland, Oregon.  Compound Interest covers the benefits of water (and other) fluoridation programs:

The enamel that coats your teeth is made up primarily of the compound hydroxyapatite. This ionic compound consists of calcium ions, phosphate ions and hydroxide ions, and is also a major component of your bones. Enamel is well known for being pretty strong, but it can be slowly broken down and lose ions from its structure under acidic conditions. This is known as demineralisation. Our body has a built-in countermeasure for this, and can replace the ions lost with ions from our saliva, in a process known as remineralisation. However, sometimes the rate at which this replacement occurs is below that at which the ions are being lost. When this happens the pores in the tooth can become enlarged, and cavities and tooth decay can result.

Fluoride ions can help arrest this process. They can be incorporated into the hydroxyapatite structure, replacing the hydroxide ions and forming fluorapatite. Fluorapatite is stronger than hydroxyapatite, and is also more resistant to acidic conditions. This means it can greatly delay the onset of cavities and tooth decay, and this is the reason why there’s a clamour to add it to water supplies.

Much more at his blog, including a nice infographic.

sunflowers have an internal clock

Sunflowers track the sun from east through west. Researchers thought they were just following the light of the sun, but experiments show that sunflowers still bend east to west when under a constant light source. From Scientific American:

It is one of the great symbols of summer: a sunflower (Helianthus annuus) bending to track the path of the Sun from east to west, straining to make the most of each day. At night, the sunflower eases back towards the east in preparation for daybreak.

Yet these flowers are not responding simply to light, but also to an internal clock, researchers have found.

Plant biologists Hagop Atamian and Stacey Harmer of the University of California in Davis grew sunflowers in a field and then transferred them to growth chambers with a fixed overhead light that was always on. The plants continued their daily journey from east to west and back for several days after the transfer, suggesting that they were not responding only to the direction of the light, but their own timekeeper.

“It brings into question whether there’s some sort of memory that’s found within the plant that allows this regulation,” says Mark Belmonte, a plant biologist at the University of Mannitoba in Winnipeg, Canada, who was not involved with the study. ”This could be a very fine-tuned process.”

Make sure you see them in action in the video.

truvia is toxic to fruit flies

Dead fruit fly. Picture from wikipedia

C&EN describes how a sixth grade science project lead to the discovery that Truvia, a sweetner from the stevia plant, is toxic to fruit flies:

The discovery wouldn’t have been possible without Simon D. Kaschock-Marenda, who went to his dad three years ago to pitch an idea. Knowing that his father was a neurobiologist at Drexel with access to a supply of fruit flies, the sixth-grader proposed a science fair project: He wanted to feed a variety of sugars and sweeteners to flies and see how the insects fared.

One of the sweeteners father and son purchased from the supermarket for testing was Truvia, made by Minneapolis-basedCargill. The pair mixed that sweetener and a number of others with Drosophila food, put each in a container with adult fruit flies, and waited.

Almost a week later, Marenda’s son pointed out that the flies in the Truvia container had died, while the ones feeding off the other sweeteners were still alive. Thinking the result might be a fluke, the youngster and his father repeated the experiment, only to obtain the same result. Flies raised on the Truvia-laced food survived for about six days, and flies fed table sugar lived around 40 to 50 days.

The research was moved into the father’s lab where he discovered that erythritol is responsible for toxicity:

[F]ruit flies given food laced with Pure Via, another sweetener derived from the stevia plant, didn’t react as they had to Truvia. Their life span was unaltered.

So O’Donnell sent Truvia off to be analyzed with high-performance liquid chromatography and got interesting results. “More than 90% of the Truvia was erythritol,” Marenda says.


To determine whether erythritol was indeed their culprit, Marenda, O’Donnell, and their team placed fruit flies in containers with increasing doses of erythritol. At the highest concentration the researchers tested—2 M erythritol—all the flies died after a day or two of feeding.